如何创建 JavaFx 应用程序实例并向其推送自己的参数？

Question

我正在尝试使用 Google 地图 Api + JavaFx 创建地图。在主 class 中，我阅读了 JSON 文件，然后创建了集群，程序的重点是将这些集群显示为标记，其中包含多个位置。所以在主 class 中，我读取了 JSON 文件，然后创建了 DBSCANClusterer clusterer = new DBSCANClusterer(coordinates, 2, 2);，我必须将它推入 class GoogleMap，其中 JavaFX 正在创建 [=17] =] 等等。我还使用它在我的 html 文件中的脚本中使用 java 代码：

JSObject jsobj = (JSObject) webView.getEngine()
             .executeScript("window");
     jsobj.setMember("BrowserJavaObject", new BrowserJavaObject(clusterer));

那么同样的事情还要在BrowserJavaObject class中进一步推进，所有的聚类计算都在这里。我试图创建 GoogleMap class 的对象，但这不起作用。那么如何让它发挥作用呢？或者这甚至可能吗？谢谢指教。

JSON主要class:

public class JsonMain {

     static List<Coordinate> coordinates = new ArrayList<>();

    private static final String ITEMS_NAME = "items";
    private static final String LATITUDE_PROPERTY = "latitude";
    private static final String LONGITUDE_PROPERTY = "longitude";
    private static final String CRASH_NAME = "em_type_name";

    static void parseCrashCoordinates(final JsonReader jsonReader, final ICoordinatesListener listener)
            throws IOException {    
        // Reading JSON file
    }

     // Collecting all coordinates in ArrayList.
    private static void testCollecting()
            throws IOException {
      //  List<Coordinate> coordinates = new ArrayList<>();
        readAndParse((lat, lng) -> coordinates.add(new Coordinate(lat, lng)));
        System.out.println(coordinates.size());   
    }

    public static void main(String[] args) throws IOException, URISyntaxException {
        testCollecting();  


     // Initialize our clustering class with locations, minimum points in cluster and max Distance
        DBSCANClusterer clusterer = new DBSCANClusterer(coordinates, 2, 2);

        GoogleMap gm = new GoogleMap(clusterer);
        gm.launch(GoogleMap.class);
    }

Google地图class:

public class GoogleMap extends Application {

private DBSCANClusterer clusterer ;

public GoogleMap(DBSCANClusterer c) {
    this.clusterer = c;
}


@Override 
public void start(Stage stage) throws MalformedURLException {

    File file = new File("C:/Users/Evgeny/git/Diploma_MSU/diploma/html/map.html");
    URL url222 = file.toURI().toURL();

     WebView webView = new WebView();
     final WebEngine webEngine = webView.getEngine();

     JSObject jsobj = (JSObject) webView.getEngine()
             .executeScript("window");
     jsobj.setMember("BrowserJavaObject", new BrowserJavaObject(clusterer));

    webEngine.load(url222.toString()); 

    // create scene
    stage.setTitle("Web Map");
    Scene scene = new Scene(webView,1000,700, Color.web("#666970"));
    stage.setScene(scene);
    // show stage
    stage.show();

} 
}

BrowserJavaObject class:

public class BrowserJavaObject {

private DBSCANClusterer clusterer ;

public BrowserJavaObject(DBSCANClusterer c) {
    this.clusterer = c;
}

public String showMarkers() {
    ArrayList<ArrayList<Coordinate>> clusters_raw= this.clusterer.performClustering();
    ArrayList<Cluster> clusters = new ArrayList<>();

    String pointsArray = " [ ";
    for(int i=0; i<clusters_raw.size(); i++) {
            Cluster c = new Cluster(clusters_raw.get(i));
            clusters.add(c);

            pointsArray += c.getLocationAsArray() + " , ";
    }
    pointsArray += "]";

    System.out.println("Number Of Clusters Created: "+clusters.size());
    return pointsArray;

}
}

map.html:

<!DOCTYPE html>
<html>
<head>
<meta charset="UTF-8">
<title>Map</title>
<meta name="viewport" content="initial-scale=1.0, user-scalable=no" />
    <style type="text/css">
        html { height: 100% }
        body { height: 100%; margin: 0; padding: 0 }
        #map_canvas { height: 100% }
    </style>
    <script async defer type="text/javascript"
            src="https://maps.googleapis.com/maps/api/js?callback=loadmap">
    </script>
</head>
<body onload="loadmap()">
<div id="map_canvas" style="width:100%; height:100%"></div>
<script>
var map;
function loadmap(){

  var options = {
      zoom: 16,
      center: new google.maps.LatLng(55.7558, 37.6173),
      mapTypeId: google.maps.MapTypeId.ROADMAP
  }
  map = new google.maps.Map(document.getElementById("map_canvas"), options);

  var markers = [];

  // Call the Java code to calculate clusters data, and save the returned clusters into a variable
  var markers_data = BrowserJavaObject.showMarkers();

  for( var i=0; i<markers_data.length; i++ ){
    var position = markers_data[i];
    var icon = "data:image/svg+xml,%3Csvg%20xmlns%3D%22http%3A%2F%2Fwww.w3.org%2F2000%2Fsvg%22%20width%3D%2238%22%20height%3D%2238%22%20viewBox%3D%220%200%2038%2038%22%3E%3Cpath%20fill%3D%22%23a22%22%20stroke%3D%22%23ccc%22%20stroke-width%3D%22.5%22%20d%3D%22M34.305%2016.234c0%208.83-15.148%2019.158-15.148%2019.158S3.507%2025.065%203.507%2016.1c0-8.505%206.894-14.304%2015.4-14.304%208.504%200%2015.398%205.933%2015.398%2014.438z%22%2F%3E%3Ctext%20transform%3D%22translate%2819%2018.5%29%22%20fill%3D%22%23fff%22%20style%3D%22font-family%3A%20Arial%2C%20sans-serif%3Bfont-weight%3Abold%3Btext-align%3Acenter%3B%22%20font-size%3D%2212%22%20text-anchor%3D%22middle%22%3E" 
                + position[2]
              + "%3C%2Ftext%3E%3C%2Fsvg%3E";

//    if(zoom > 11) icon = null; //Default to marker with no number if at city zom level

    markers.push( new google.maps.Marker({
                    position: new google.maps.LatLng( position[0], position[1] ),
                    map: map,
                    title: position[2],
                    text: position[2],
                    icon: icon
                }) 
    );
  } 
}
</script>
</body>
</html>

所以地图已加载，但那里没有集群。最终所有这些聚类方法都没有被调用，因为我的 clusterer 对象没有在其他 class 中进一步传递。

非常感谢！

Answer 1

您使用 Application class 的方式有误。 Application class 代表您的整个应用程序并负责其生命周期；特别是它有一个 start() 方法，当通过调用 launch() 启动 JavaFX 工具包时，它会为您调用。 Application class 并不代表您的 UI 的特定部分（这就是您的 GoogleMap class 的用途）。

所以你应该使 JsonMain 成为 Application 的子 class，而不是 GoogleMap，并且你应该将启动代码移动到（恰当命名的）start()方法：

public class GoogleMap {

    private DBSCANClusterer clusterer ;

    private final WebView view ;

    public GoogleMap(DBSCANClusterer c) throws MalformedURLException {
        this.clusterer = c;

        File file = new File("C:/Users/Evgeny/git/Diploma_MSU/diploma/html/map.html");
        URL url222 = file.toURI().toURL();

        view = new WebView();
        final WebEngine webEngine = webView.getEngine();

        JSObject jsobj = (JSObject) webView.getEngine()
                 .executeScript("window");
        jsobj.setMember("BrowserJavaObject", new BrowserJavaObject(clusterer));

        webEngine.load(url222.toString()); 

    } 

    public Node getView() {
        return view ;
    }

}

和

public class JsonMain extends Application {

    static List<Coordinate> coordinates = new ArrayList<>();

    private static final String ITEMS_NAME = "items";
    private static final String LATITUDE_PROPERTY = "latitude";
    private static final String LONGITUDE_PROPERTY = "longitude";
    private static final String CRASH_NAME = "em_type_name";

    static void parseCrashCoordinates(final JsonReader jsonReader, final ICoordinatesListener listener)
            throws IOException {    
        // Reading JSON file
    }

     // Collecting all coordinates in ArrayList.
    private static void testCollecting()
            throws IOException {
      //  List<Coordinate> coordinates = new ArrayList<>();
        readAndParse((lat, lng) -> coordinates.add(new Coordinate(lat, lng)));
        System.out.println(coordinates.size());   
    }

    public static void main(String[] args) {
        launch(args);
    }

    @Override
    public void start(Stage stage)  
        throws IOException, URISyntaxException, MalformedURLException {

        testCollecting();  


     // Initialize our clustering class with locations, minimum points in cluster and max Distance
        DBSCANClusterer clusterer = new DBSCANClusterer(coordinates, 2, 2);

        GoogleMap gm = new GoogleMap(clusterer);

        // create scene
        stage.setTitle("Web Map");
        Scene scene = new Scene(gm.getView(), 1000, 700, Color.web("#666970"));
        stage.setScene(scene);
        // show stage
        stage.show();

    }

}

您可能应该进一步重构以正确分离您的关注点；例如解析数据等可能不是 Application class 的工作。但这至少可以让您将参数传递给 GoogleMap class 并让您启动以预期的方式应用程序。

如何创建 JavaFx 应用程序实例并向其推送自己的参数？

How to create instance of JavaFx application and push there own parameters?

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